The present invention relates to a biological signal drawing apparatus and method in which a waveform on the basis of a biological signal such as a brain wave signal is displayed on a screen such as a displaying device, or printed by a printer.
A biological signal waveform which is typified by an electroencephalogram or an electrocardiogram is output onto recording paper or the like by an ink recorder, and then used in clinical examination by doctor. Recently, moreover, a paperless electroencephalograph or electrocardiograph has been advanced, and a biological signal such as a brain wave signal is digitized, so that, for example, the digitized signal is sent to a displaying device and an electroencephalogram is displayed on a screen.
In a display in which such digital data are drawn on a screen, a line segment is expressed as a set of pixels, and therefore it is often that the impression of the waveform is different from that of a waveform which is drawn on recording paper by using an ink recorder that analogly performs drawing.
This is caused by the phenomenon that the elasticity and frequency characteristics of a pen of the ink recorder cause the pen not to be able to respond to very small noises, and in contrast even such noises are faithfully drawn in the drawing of the digital data on the screen.
Therefore, doctors who have reviewed an electroencephalogram on recording paper point out that an electroencephalogram displayed on a screen appears different from that on recording paper, and an electroencephalogram on recording paper in noiseless and looks clear. Therefore, it is requested to develop a biological signal drawing apparatus which can perform a waveform display that is similar to drawing on recording paper. There is a similar problem also in the case where a waveform is printed by a printer in addition to display.
In order to smoothly draw an electroencephalogram, it is contemplated that the smoothing technique is applied to the drawing. In the case where the smoothing technique is simply applied to the drawing, however, there is a possibility that smoothing affects waveform drawing of a characteristic change of a biological signal waveform, such as spikes in an electroencephalogram.
By contrast, in view of a problem that an abnormality cannot be found unless a waveform is printed out, a solution has been taken in which a format (a two-dimensional pattern) of recording paper is displayed on a monitor (see JP-T-10-509331). However, a waveform is drawn by a related-art technique, and the drawn waveform is not made close to a waveform which is drawn by an ink recorder (see JP-T-10-509331).